Equine coat color genetics
Equine coat color genetics determine a horse's coat color. Many colors are possible, but all variations are produced by changes in only a few genes. Bay is the most common color of horse, followed by black and chestnut. A change at the agouti locus is capable of turning bay to black, while a mutation at the extension locus can turn bay or black to chestnut.
Before domestication, horses are thought to have had these coat colors.
The flat, earthy tone of the coat and vivid dorsal stripe are indicative of the D allele. Primitive markings are seldom visible on horses without the dominant, wildtype dun allele (D).
Image: Kamsin 0028
Image: Friesian Sporthorsestallion
The horse is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of Equus ferus. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature, close to Eohippus, into the large, single-toed animal of today. Humans began domesticating horses around 4000 BCE, and their domestication is believed to have been widespread by 3000 BCE. Horses in the subspecies caballus are domesticated, although some domesticated populations live in the wild as feral horses. These feral populations are not true wild horses, which are horses that never have been domesticated and historically linked to the megafauna category of species. There is an extensive, specialized vocabulary used to describe equine-related concepts, covering everything from anatomy to life stages, size, colors, markings, breeds, locomotion, and behavior.
Horse
Points of a horse
Size varies greatly among horse breeds, as with this full-sized horse and small pony.
Bay (left) and chestnut (sometimes called "sorrel") are two of the most common coat colors, seen in almost all breeds.